Mobile Wi-Fi is surprisingly easy. First, I'm not an advocate of hopping on someones unsecured connection. It's stupid of them to leave it unsecured, but I personally don't feel it's right to "use" their connection because it's there... but that's just me :shakin: If you pay for the connection, you know it will work and you can often get plans from major providers that will allow you to use a national chain of hotspots.
Now to the fun stuff... Most modern cities are covered with hotspots and the range is usually about 300 + feet from the transmitter. That isn't the best range if you want to stay in your truck. You can go out and buy a stonger antenna, but it's more fun to build one yourself. There are some really cool home brew antennas for Wi-Fi and some actually work really, really well.
Here are two of my favorite cheap homebrew antennas:
Chinese Cookware antenna
Tin Can Antenna (Cantenna for short)
Pete